Construction And Analytical Application Of Simple Electrochemical Sensors Based On Small Molecules Signal Amplification

1 IntroductionFirstly,the characteristics and detection methods of several small molecular substances are introduced.Then the overview,classification of electrochemical sensors and electrochemical methods are introduced in detail,with emphasis on the progress of signal amplification technology.Finally,the main purpose and content of this paper are briefly introduced.2 Electrochemical method for simultaneous detection of ascorbic acid,dopamine and uric acid based on Heme signal amplificationIn this chapter,Heme,Fc[CO-Cys（Trt）-OMe]_2,（[Fc（Cys）₂]）and Fc[CO-Glu-Cys-Gly-OH],（[Fc-ECG]）were directly modified on the glassy carbon electrode（GCE）by electrochemical deposition.Three kinds of sensors,such as Heme/GCE,Fc（Cys）₂/GCE,Fc-ECG/GCE,were prepared.The sensors were characterized by SEM,TEM and DPV,and their electrocatalytic activities against ascorbic acid,dopamine and uric acid were investigated.The experimental results showed that the sensor Heme/GCE had good electrocatalytic activity,it can realize the separation of oxidation peaks and signal amplification of three substances（ascorbic acid,dopamine,uric acid）.Based on this,an electrochemical method for the simultaneous detection of ascorbic acid,dopamine,uric acid was established.It can be obtained linear responses for AA,DA and UA in the following concentration ranges:10-50,5-20 and 2.5-20μmol·L^-1,and the limits of detection were calculated as 0.76,0.50 and 0.63μmol·L^-1,respectively.The selectivity,repeatability,stability and accuracy of the sensor were investigated.The sensor was applied to the simultaneous detection of ascorbic acid,dopamine and uric acid in human serum samples with satisfactory results.3 Electrochemical method for the detection of Bisphenol A based on Heme signal amplificationIn this chapter,Heme,Dopamine（DA）,β-cyclodextrin（β-CD）and ferrocenylglutathione（Fc-ECG）were directly modified on the screen printed electrode（SPE）by electrochemical deposition.Four kinds of biosensors,such as Heme/SPE,DA/SPE,β-CD/SPE,Fc-ECG/SPE,were prepared.The sensors were characterized by SEM,DPVand EIS,and the electrocatalytic activity of the biosensors for bisphenol A was investigated.The experimental results showed that Heme/SPE had good electrocatalytic activity.An electrochemical method for the determination of bisphenol A（BPA）was established.The current response vs concentration of BPA showed a linear relationship in the range of 0.05-0.50μmol·L^-1,the limit of detection as5.0 nmol·L^-1.The selectivity,repeatability,stability and accuracy of the sensor were investigated.The sensor was used to detect BPA in environmental water samples with satisfactory results.4 Electrochemical method for simultaneous detection of uric acid and folic acid based on Ferrocene amino acid signal amplificationIn this chapter,β-cyclodextrin（β-CD）,Heme and ferrocenylglutathione（Fc-ECG）were directly modified on the glassy carbon electrode（GCE）by electrochemical deposition.Three kinds of sensors,such asβ-CD/GCE,Heme/GCE and Fc-ECG/GCE,were prepared.The sensors were characterized by DPV.The electrocatalysis of the sensors for uric acid and folic acid was investigated.The experimental results showed that the sensor Fc-ECG/SPE had good electrocatalytic activity.Based on this,an electrochemical method for the simultaneous detection of uric acid and folic acid was established.It can be obtained linear ranges for UA and FA were all 10-500μmol·L^-1,and the limits of detection were calculated also as 3.33μmol·L^-1.The selectivity,stability and accuracy of the sensor were investigated.The sensor was applied to the simultaneous detection of uric acid and folic acid in human serum samples with satisfactory results.5 Electrochemical method for the detection of nitrite（NO₂^-）based on Ferrocene amino acid signal amplificationIn this chapter,two ferrocene derivatives,Fc[CO-Cys（Trt）-OMe]_2,（[Fc（Cys）₂]）and ferrocenylglutathione（Fc-ECG）were directly modified on the screen printed electrode（SPE）by electrochemical deposition.Two kinds of sensors Fc（Cys）₂/SPE,Fc-ECG/SPE were prepared.The sensors were characterized by SEM,CV and DPV,and the electrocatalytic activity of the sensors for nitrite was investigated.The experimental results showed that the sensor Fc-ECG/SPE had good electrocatalytic activity and can amplify the oxidation peak signal of NO₂^-.An electrochemical method for the determination of NO₂^-by Fc-ECG/SPE sensor was established.The linear range was 1.0-50μmol·L^-1,and the detection limit was 0.33μmol·L^-1.The selectivity,repeatability,stability and accuracy of the sensor were investigated.The sensor was applied to the detection of NO₂^-in human serum and real samples of pickled juice with satisfactory results.6 Electrochemical method for the detection of Heme based on ferrocenyldicarboxylic acid signal amplificationIn this chapter,the electrochemical properties of ferrocenyldicarboxylic acid（Fc（COOH）₂）in NaOH solution and three organic solvents（acetonitrile,ethanol,dichloromethane）are studied.The experimental results showed that the redox current had a linear relationship with the square root of the scanning rate,and the electrochemical behavior was diffusion controlled.There is intermolecular force between Fc（COOH）₂ and Heme.The combination of them makes the molecular chain lengthen,the electron transfer rate slow down and the current decrease.Due to the poor electrochemical signal of Heme,based on the current signal of Heme enhanced by Fc（COOH）₂,a new electrochemical method for the detection of Heme with Fc（COOH）₂ as electrochemical probe was established.The linear range was 1.0-5.0μmol·L^-1,and the limit of detection was 0.7 nmol·L^-1.The selectivity and accuracy of the method were investigated.The sensor was used to detect Heme in human serum samples with satisfactory results.7 Research meaningIn this paper,heme,ferrocene derivatives and other electronic mediators were directly modified on the surface of the electrode or placed in the test solution to build a marker free electrochemical sensor.The electrochemical sensors were simple to build,and the electronic mediators play a role in accelerating the electronic transfer between the electroactive substance and the electrode,to achieve the electrochemical signal amplification,and to be specifically identified directly according to the target analyte.The change of electrochemical signal caused by the former and the latter can be detected quantitatively.Simple,rapid,sensitive and highly selective electrochemical methods for the determination of common small molecules were established.